A technology which takes environmental information or the like into an ICT (Information and Communication Technology) net such as the internet and an information processing system and utilizes has been developed.
For example, in a residence and an office, a system that power consumption of electrical appliances is measured and the user can always check the power consumption of a building has been developed.
A system to control a power supply using measured power consumption, and reduce power consumption automatically has been developed. A system which controls air-conditioning equipment, a lighting apparatus and a light shielding apparatus most suitably by making a measured value of power consumption cooperate with a measured value by such as a temperature sensor, humidity sensor and an illumination sensor has been also proposed.
In order to realize these systems, a finer granularity sensing technology which uses a lot of several kinds of sensor apparatuses becomes important. In the finer granularity sensing technology, cost cutting and a miniaturization of an apparatus become important.
For example, in order to perform a sensing with high accuracy, for a sensor apparatus equipped with a battery, a large capacity battery is required and periodical battery exchange is needed. Cost becomes high when using a large capacity battery. Because the periodical battery exchange is needed, convenience is low.
Accordingly, various technologies for obtaining an electric power from an existing alternating current power network are proposed. For example, a technology which performs smooth stabilization of alternating current power acquired from an alternating current power network and acquires direct-current electricity is proposed by patent document 1. An apparatus of power-saving which supplies an electric power to a radio communication control unit only for a communication period is proposed by patent document 2.